"We're delighted to deepen our partnership with AppNexus, which has proven itself as a clear leader in ad tech and a company with the scale and ingenuity to continue to transform our industry."

Brian O'Kelley, the chief executive of AppNexus said: "Publishers want a technology partner they can trust. Open AdStream has been one of the most effective and trusted ad serving platforms in the world for years. We're going to make it number one in programmatic."